A good photograph can speak volumes about its subjects, yet still leave you wanting to know more.

The acclaimed and prolific American photographer Mary Ellen Mark, who died May 25 at the age of 75, was known for her humanist portraits: homeless children in Seattle, prostitutes in India, a family living out of its car. In 1990, she took one of her most memorable shots, titled Amanda and her cousin Amy.

“This photograph raises a lot of questions and leaves me with a slightly uneasy feeling,” says Jeff Jacobson, a New York photographer and a friend of Mark’s. “That, I feel, over and over again is the hallmark of her best work.”

The Nenets — who live at daily temperatures of -35°C (-31°F) in northern Siberia, wash just once a year and eat raw reindeer liver to survive — are documented in beautiful black and white monochrome photographs made by photographer Sebastião Salgado, possibly the best-loved photojournalist in the world.

Reviewer Laura Cummings says of his subjects:

These people endure the coldest temperatures imaginable. They stand like statues, apparently frozen still, positioned against the snowbound winds that drive the snow across the picture in silvery blizzards. They stand, and they withstand.